tirebouchon69 wrote:
Hi,
I want to modify an old ICOM IC-22s vhf radio for APRS at 144.390 MHz. I
already made the 10 KHz step modification, and now I need to make it cover
the lower part of the band, and this is where I get a problem:
If I set binary code "0" on diode matrix, I should get 144.390 MHz exactly,
but the VCO doesn't work at this low frequency (even if indector vco is
re-tuned). I see 2 possibilities:
1- Change X2 crystal 44.56333 MHz for a lower crystal. For exemple, a
44.250 MHz would make the rig start at 143.450 MHz, and binary code "94"
would generate 144.390 APRS frequency. Any crystal between 44.0 & 44.5 MHz
would be fine. Where could I find such a crystal? (Digi-Key has nothing
around 44.0 to 44.5 MHz Xtals)
2- Modify VCO circuit to make it work lower (changing D3 varicap, C40 or L7
probably?). Did someone try this before?
Thank you in advance.
-------------------------------------------
Daniel VE2BAP
Montréal (Roxboro), Québec, Canada
It's been a while, but I'm sure I didn't change any xtals.
mike
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